The invention relates to devices for holding wafer-shaped articles, such as semiconductor wafers.
Semiconductor wafers are subjected to various surface treatment processes such as etching, cleaning, polishing and material deposition. To accommodate such processes, a single wafer may be supported in relation to one or more treatment fluid nozzles by a chuck associated with a rotatable carrier, as is described for example in U.S. Pat. Nos. 4,903,717 and 5,513,668.
The patents referenced above operate on the Bernoulli principle, such that the wafer receives subjacent support from a gas cushion rather than by contact with the chuck. Such chucks nevertheless ordinarily include a circular series of pins that are positioned radially outwardly of a wafer positioned on the chuck. Those pins prevent lateral displacement of the wafer relative to the chuck.
As described in U.S. Pat. No. 4,903,717, each pin projects upwardly from a respective pivotal base. The axes of the pin and base are vertical but offset from one another such that pivoting of the base causes the associated pin to travel along a circular arc and hence be adjustable in its radial position. The pivot bases are each provided with gear teeth, which mesh with the teeth of a common gear ring that is coaxial with the axis of rotation of the chuck. Rotation of the gear ring relative to the chuck thus causes all of the pins to move conjointly and to the same extent.
That construction permits the pins to be moved radially outwardly for placement or removal of a wafer, and then to be moved radially inwardly to be brought into contact with the peripheral edge of a wafer. Such contact prevents not only lateral displacement of the wafer relative to the chuck, but also relative rotation between the wafer and chuck as the chuck is spun.
Other spin chucks operate under control of magnetic fields, by fashioning the chuck body as a magnetic rotor positioned coaxially within a surrounding annular magnetic stator, as described for example in U.S. Pat. No. 6,485,531. In such chucks the rotary head supports the wafer. The present assignee has designed such chucks utilizing pins having characteristics in common with those described above, but which serve in this context also to support the weight of the wafer.
Spin chucks are subjected to extreme temperatures and highly acidic etching solutions in use. Designs that perform without incident under one set of processing conditions might perform with less consistency under different processing conditions.